Export participants to different formats

* CSV
* PDF (requires Python dependency `weasyprint`)
* ODS (requires Python dependency `pyexcel_ods3`)

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

lib/mobilizon/export.ex

@@ -0,0 +1,57 @@
+defmodule Mobilizon.Export do
+  @moduledoc """
+  Manage exported files
+  """
+
+  use Ecto.Schema
+  import Ecto.Changeset
+  import Ecto.Query, only: [where: 3]
+  alias Mobilizon.Storage.Repo
+
+  @type t :: %__MODULE__{
+          file_path: String.t(),
+          file_name: String.t() | nil,
+          file_size: integer() | nil,
+          type: String.t(),
+          reference: String.t(),
+          format: String.t()
+        }
+
+  @required_attrs [:file_path, :type, :reference, :format]
+  @optional_attrs [:file_size, :file_name]
+  @attrs @required_attrs ++ @optional_attrs
+
+  schema "exports" do
+    field(:file_path, :string)
+    field(:file_size, :integer)
+    field(:file_name, :string)
+    field(:type, :string)
+    field(:reference, :string)
+    field(:format, :string)
+
+    timestamps()
+  end
+
+  @doc false
+  def changeset(export, attrs) do
+    export
+    |> cast(attrs, @attrs)
+    |> validate_required(@required_attrs)
+  end
+
+  @spec get_export(String.t(), String.t(), String.t()) :: t() | nil
+  def get_export(file_path, type, format) do
+    __MODULE__
+    |> where([e], e.file_path == ^file_path and e.type == ^type and e.format == ^format)
+    |> Repo.one()
+  end
+
+  @spec outdated(String.t(), String.t(), integer()) :: list(t())
+  def outdated(type, format, expiration) do
+    expiration_date = DateTime.add(DateTime.utc_now(), -expiration)
+
+    __MODULE__
+    |> where([e], e.type == ^type and e.format == ^format and e.updated_at < ^expiration_date)
+    |> Repo.all()
+  end
+end